1. Field of the Invention
Embodiments of the invention relate to a method and apparatus for contacting a substrate, and more particularly, to a method and apparatus used to contact a substrate during an electrochemical plating process.
2. Background of the Related Art
Metallization of sub-quarter micron sized features is a foundational technology for present and future generations of integrated circuit manufacturing processes. More particularly, in devices such as ultra large scale integration-type devices, i.e., devices having integrated circuits with more than a million logic gates, the multilevel interconnects that lie at the heart of these devices are generally formed by filling high aspect ratio, i.e., greater than about 4:1, interconnect features with a conductive material, such as copper, aluminum, nickel, gold, or other conductive material. Conventionally, deposition techniques such as chemical vapor deposition (CVD) and physical vapor deposition (PVD) have been used to fill these interconnect features. However, as the interconnect sizes decrease and aspect ratios increase, void-free interconnect feature fill via conventional metallization techniques, i.e., PVD and CVD, for example, becomes increasingly difficult. Therefore, plating techniques, i.e., electrochemical plating (ECP) and electroless plating, have emerged as promising processes for void free filling of sub-quarter micron sized high aspect ratio interconnect features in integrated circuit manufacturing processes.
In an ECP process, for example, sub-quarter micron sized high aspect ratio features formed into the surface of a substrate (or a dielectric layer deposited thereon) may be efficiently filled with a conductive material, such as copper. ECP plating processes are generally two stage processes, wherein a seed layer is first formed over the surface features of the substrate or dielectric layer, and then the surface features are exposed to an electrolyte solution, while an electrical bias is applied between the seed layer and a copper anode positioned within the electrolyte solution. The electrolyte solution generally contains ions to be plated onto the surface of the substrate, and therefore, the application of the electrical bias causes these ions to be urged out of the electrolyte solution and to be plated onto the electrically biased seed layer.
Conventional electrochemical plating cells utilize a contact element or contact ring that is configured to electrically engage a perimeter of the substrate surface in order to supply the electrical plating bias required to initiate and sustain plating operations. However, one drawback to this configuration is that when the substrate surface is immersed in the plating solution, the electrical contacts also generally contact the plating solution, and as a result thereof, metal ions in the solution are generally plated on the electrical contacts themselves and not on the substrate surface. In order to overcome this challenge the plating industry has attempted to provide contact elements that have a dry contact-type configuration. i.e., the electrical contact or contacts are generally surrounded by a seal that prevents the plating solution from touching the contact pins. Dry contact configurations show promise in that they are designed to isolate the electrical contact elements from the plating solution, which prevents metal ions in the solution from plating on the electrical contact elements. However, one challenge associated with dry contact configurations is that the pressure differential between the region where the plating solution is contained and the sealed region surrounding the electrical contacts has been shown to be prone to solution leakage, which eliminates the advantages provided by the dry contact configuration.
Therefore, there is a need for a dry electrical contact element for a substrate plating apparatus, wherein the dry electrical contact element overcomes the challenges associated with pressure differential driven fluid leakage across the dry contact seals.